Telephone switching system



Aug. 5, 1924s F. M. SLOUGH TELEPHONE SWiTCHING SYSTEM Original Filed May6, 1918 /imm i Patented Aug. 5, 1924.

FRANK M. SLO'UGH, OE ROCHESTEE, NEW YORK, ASSlfG-NOR TO THESTROMBERG-GARL SON TELEPHONE MANUFACTUBING COMPANY, OF ROCHESTER, NEWYORK, A COR- TELEPI IONE SWITCHING SYSTEM.

Application filed May 6,

To all whom it may concern:

Be it known that I, FRANK M SLQUGH, a citizen of the United States, andresiding at Rochester, in the county of Monroe and State of New York,have invented certain new and useful Improvements in Telephone SwitchingSystems, of which the following is a full, clear, concise, and exactdescription.

This invention relates to telephone switclr ing systems, and: moreparticularly to a form of telephone switching system particularlyapplicable to subscriber or sfo-c'alled automatic telephone systems, inwhich the central office line interconnecting. apparatus is controlledby current impulses delivered over the two sides of the line in series,and acting through the medium of the so-oalled fast and slow relays tocontrol the selector and connector switches of the exchange.

It has been the common practice to have these fast and slow relaysresponsive, respectively, to interruptions of the line circuit and to aseries of such interruptions. The well-known type of subscriber operatedswitch for example, has a controlling relay Which sends a currentimpulse to a primary switch operating magnet at each interruption of theline circuit. At the same time impulses are sent to a slow relay whichenergizes at the 'first impulse and retains its armature in its operatedposition during a series of impulses. At the end of the series ofimpulses, the slow relay retracts its armature thereby completing acircuit, whereby the switch Wipers are stepped ordinarily by a secondaryoperating magnet to automatically select an idle line of a group firstselected by the primary switch operating magnetf The above refers moreparticularly to what are known as selector switches, and in theoperation of connector switches a similar organism is used to control. aso-called side switch, theside switch being advanced after a series ofimpulses to local connector switch circuits to suitably control thesecondary movement of the connector switch in preparation for the nextseries of impulses to move the secondary switch wipers to a lineconnectinglposition.

In the system of invention I propose to accomplish the switchingfunction,- whereby the selector switch is'controlled in its 1918. SerialNo. 232,963.

primary or secondary movements, or whereby connector swltches arecontrolled 1n their primary and secondary movements by the use of asingle relay of unitary structure having two armatures, the one of whichis responsive to the short impulses of current passing through thewinding of the relay, and the other of which can only operate on acurrent impulse continuing for a predetermined length of time. Such arelay as is described and claimed in my application, Serial No. 135,636,filed December 7, 1916, is capable of such a use. Other relays which maybe made to perform in a way suitable to the requirements of. the presentinvention are the Ghegan type of relays which are very commonly used intheart of telegraphy, according to the wcllknown Ghegan two-way repeatersystem. i It is an object of my invention to simplify the wiring andoperation of selector and connector switches of automatic exchanges bythe use of such a relay to control their operation to simplify thewiring,the space occupied, and to make the operation'more positive.

Other objects of my invention and the invention itself will be apparentas the de scription thereof progresses.

Referringto the drawing accompanying this specification, at A, I show acalling substation instrument having a subscribers switch a, the usualtalking apparatus illustrated in the conventional way, and aconventional representation of a subscribers line circuit interrupter,or commutator of the usual type, the circuit of the line being extendedto the central oflice switching apparatus by line conductors 1 and 2.Certain parts of the central office switching apparatus as are notnecessary to a full understanding of my invention are omitted as, forinstance, the line finder switch mechanism containing the switch wipers3, and line con tacts 4, It is understood that these switch wipers andcontacts will be. brought into association in any desired manner. 7 isthe impulse relay by means of which the actuating impulses aretransmitted to the stepping magnets of the first selector switch, withwhich it is associated.

If the present invention were employed operated by the central operatorssending device instead of impulses transmitted from the callingsubscribers station. The side switch employed in illustrating thepresent invention is of such a nature that it moves its wipers upon theenergization of its actuating magnet. A side switch operating in such amanner is disclosed in an application of Oscar F. Forsberg, Serial No.6302, filed Feby. th, 1915, Patent No. 1,252,420, January 8, 1918. Theside switch herein disclosed is moved from position 1 to position 2 uponthe first energization of its controlling escape magnet, from position 2to pos1- #7 tion 3 upon the second energization thereof and fromposition 3 to position 4 upon the third energization of its escapemagnet. A fifth position for the side switch wiper is provided in thecase of the side switch used in the connector circuit, whereas the sideswitch used in connection with the selector circuit herein illustratedhas only four positions.

In connection with the selector switch of my invention, at PM I show aprimary step-- ping magnet therefor, adapted to step the selector switchwipers from contact level to contact level under the control of thesubstation interrupter shown at I. At SM is shown a secondary steppingmagnet for the selector switch and which magnet is adapted to step theselector switch wipers from one set of contacts to another in a givenlevel to which they have been previously directed under the control ofthe subscribers interrupter I by the primary magnet PM. The secondarymagnet SM, automatically produces its own circuit interruptions wherebythe stepping action is automatically continued. A release magnet for theselector switch is shown at RL, adapted when operated by a prolongedimpulse of current to restore the selector switch mechanism to itsnormal un-operated position. At Esc is shown an escape ma net adaptedupon its energization to move t e side switch wipers 5, 6, 8, 9, and 11,from one position to the next succeeding position. At 12 is shown arelay having two a-rmatures, each of which is adapted tobe operated inadistinct manner, the first armature 13 being responsive to short andlong current impulses as used in systems of the type described, and thesecond armature 14 being only responsive when the current impulsethrough the winding of the relay has been continued for a certainpredetermined length of time.

The apparatus of the connector C is in general very much like theapparatus of the selector S, the two-armature relay being shown at 15,the release magnet at RL the impulse relay at 16, the primary steppingmagnet at PS, and the secondary stepping magnet at SS in the connectorswitch. The secondary stepping magnet operates under the control of thesubscribers dial or the circuit interrupter I just as is the case withthe primary stepping magnet, and does not operate automatically as isthe case with the stepping magnet of the selector switch. The escapemagnet controlling the operation of the side switch wipers 17, 18, 19,20, 21 and 22 is shown at E802. The called subscribers telephone isshown at B, and is connected by line conductors 23 and 24 to theconnector switch contacts, such as 25 and 26 at the central oflice. Theconnector switch wipers shown in the drawing adapted to cooperate withthese connector switch contacts are shown at 27 and-28. At 29 is shown amagnet individual to the calling subscribers line. At 30 is shown aringing generator and adapted to be connected through the circuits ofthe connector switch, to the called subscribers line at a suitablepointin the operation of the circuit. I A busy signal interrupter isshown at 31.

The operation of the above-mentioned apparatus andother apparatus notmentioned, will be made clear from a description of the operation of thecircuits involved when a connection is established between the callingsubscribers station A and the called subscribers station B. Upon thesubscriber at A making a call, we will assume that the calling line hasbeen by suitable means, such as by interconnection of the wipers 3 andthe contacts 4:, extended to the side switch wipers 5 and 6 of theselector switch S. A circuit is thereby completed including thesubscribers impulse relay 7, and the central oilice source of current32, which current flowing through the windings of the impulse relay andover the telephone line to the sub scribers instrument, will cause theimpulse relay '7v to attract its armature which closes contacts 33 andopens contacts 34. The closing of the contacts 33 causes the operationof the relay 12 by the central ofiice source of current thereby includedin its circuit, and the relay 12 will thereupon attract its armatures 13and 14 one after the other in the order mentioned, the armature 13 beinga quickly responsive armature and the armature 1 1 being, as has beenmentioned, a slow acting armature. After these armatures are operated, acircuit is completed including the central office source of current forthe escape magnet E30 which operates to ad Vance the switch wipers 5, 6,8, 9, l0 and 11 from position 1 to position 2, in which position theprimary steppingmagnet PM is functioned to operate to advance theselector switch wipers 35, 36 and 37 in the primary direction ofmovement. The subscriber thereupon operating his circuit interrupter I,shown conventionally in the drawing as a dial interrupter to break andmake the circuit of the line thereby de-energizes and energizes theimpulse relay 7 a predetermined number circuit and the consequent firstde-energization of the impulse relay 7, the contacts 33 in, the circuitof the two-armature relay 12 will be opened, and the contacts 34momentarily closed. The side switch wiper beingin second positionhowever, the closing ofthe contacts 34 at this time will befunctionless. The opening of the contacts 38, however, for a very briefinterval will cause the armatures 13 and 14 to be momentarily restoredto their normal positlon.

Followingthe brief de-energization of the relay 7,\by the first breakingof the line circuit by the subscribe-rs circuit interrupter I, therewill be a momentary closure of the line circuit by the continuedoperation of the subscribers interrupter 1, during which momentaryclosure the fast armature 13 of the relay 12 willbe operated, but thetime of closure will not be long enough to permit the closure of thearmature 14, so that momentarily therewill be a circuit completedincluding the normally opened contacts of the armature 13 andthenormally closed contacts 39 of the armature 14, the circuit alsoincluding the second position contacts of the side switch wiper 10 andthe second position contacts of the side switch wiper 9, togetherwith'the primary stepping magnet PM and the central ofiice source ofcurrent. Current from thesaid source momentarily flowing over thiscircuit, will cause a momentary actuation of the primary steppingmagnetPM to advance the wipers 8 5, 36 and 37 of the selector switch S, onestep.

Following the first actuation of the primary stepping magnet PM, theofl-normal contacts 41 and 42 of the selector switch S will be closed tocondition the selector switch release magnet BL, and to condition theescape magnet'Esc respectively for operation. The subscriber may makeonly the single interruption of the line circuit to select the firstlevel of selector switch contacts, or, the circuit interruptions maycontinue until more than one circuit interruption has been made, In thisdescription we will assume that a plurality of circuit interrupt-ionsare made in rapid succession, so

that between the circuit interruptions there will be short energizationsof the two-armature relay 12 under the control of the imlastenergization which is prolonged, however, the armature 14 will beoperated, causing the escape magnet to be again actuated. The circuitfor the escape magnet at this time includes the central otfice source ofcurrent, the winding of the escape magnet, the second position contactsof the side switch wiper 11, the oit-normal contacts 41 of the selectorswitch and the normally opened contacts 43 and 40 of the two armaturesof the relay 12 which are now closed.

The escape magnet being again actuated will cause all of the side switchwipers of the first selector switch to be advanced into their thirdposition. At this time it will be noted that the release magnet BL iscaused to be very slow acting. so that it will only operate on aprolonged flow of current and on such short closures of this circuit asmay be caused by the short interrupt-ions of the line circuit under thecontrol of the subscriber as previously described, will not cause it tooperate even though at such times its circuit may becompleted throughthe momentary closure of the contacts 44 of the relay 12.

vVhen the side switch wipers 9 and 10 attain their third position asdescribed, a circuit is closed for the secondary stepping magnet SMincluding its own normal contacts 45, the central otfice source ofcurrent and the third position contacts of the switch wipers 9 and 10,so that the switch wipers reaching the third position as has beendescribed, the secondary stepping magnet will operate, and breaking itsown circuit will automatically release which will close its circuit, andthe actuation continuing it will intermittently be actuated and releaseda number of times until the selector switch wipers 35, 36 and 37 havemade contact with a non-busy connector switch circuit. This isdetermined when the selector switch wiper 37 encounters acontact whichis con" nected to the ground pole of the central office source ofcurrent under the control of apparatus in the idle connector circuit,the presence or absence of such a ground indicating the idle or busycondition of the associated connector circuit.

Vi e will assume that the connector circuit C is such an idle connectorcircuit. The contact 46 is connected to ground to indicate such an idlecondition through normal contacts 47 of the release magnet RL andthrough the first position contacts of the connector side switch wiper19 and normal contacts 51 of the special two-armature relay 15 of theconnector switch. Ground thus applied to the contacts 46 will beextended to the selector switch wiper 37 and through the third positioncontacts of the side switch wiper 11 of the selector switch, through theescape magnet to the negative pole of the central office source and inaddition will allow the side switch wipers 5, 6, '8, 9, and 11 to beadvanced into their fourth or last operative positions. hen so advanced,connection is made between the talking conductors 1 and 20f the callingline and the selector switch wipers 35 and 36, the connection extendingthrough the fourth position contacts of selector side switch wipers 5and 6. At the "same time the selector impulse relay 7 is disconnectedfrom the line circuit, since its connection therewith is only possiblethrough the first three positions of the lastnamed side switch wipers.The relay 12, as

- well as the relay 7 will be de-energized restoring its armatures tonormal position. The stepping magnet for the selector switch is alsoleft out of operative circuit due to the fact that this circuit includes'only third position contacts of the side switch wiper 10 which is nowadvanced to its fourth position.

Means are provided consisting in part-of the contacts 52 of the escapemagnet topro- ---vide for the continued closure of its circuit duringthe last named operation for a brief interval, or until the associatedapparatus involved has attained its full operated position. ,Thus, theescape magnet Esc may =have its circuit continued through the fourthposition of the said switch wiper 11, through its normally openedcontacts 52, and through the selector switch contacts 37 and .46, thenormal contacts 457 of the con- -nector release magnet-RU, firstposition contacts of the connector side switch wiper 19, and normalcontacts 51 of the connector switch two-armature relay 15. As soon asthe line circuit, however, is extended to the selector switch wipers 35and 36 as has been described, the circuit will be still further extendedthrough the said wipers, and through contacts 5 1 and 55 to the windingsof the connector switch impulse relay 16, which corresponds in itsfunctions much to the impulse relay 7 of the selector switch. Currentfrom the central office source will flow through the windings of theimpulse relay 16 and over the line circuit of the calling line toenergize the relay 16, attracting its armatures and closing its contacts56, which being closed cause the operation of the two-armature relay 15.The two-armature relay 15 is constructed and operates in the same manneras the two-armature relay 12 whose operation has been described, therelay 15 attracting its armatures will in terrupt the connection toground which has been described as being established through thecontacts 51 of the relay 15, and which caused the operation of theselector switch escape magnet Esc. The escape magnet E30 will thereuponbe restored to normal.

At this stage of the operation all of the magnets of the selector switchare de-energized, and the selector side switch wipers" are in fourth orultimate position. The op eration of the two-armature relay 15 at thisthrough its contacts, through the first position contactsof the sideswitchwiper 21 of the connector switch and the'escape magnet E802 to thenegative pole of battery, thus causing the operation of the last-namedescape magnet. The connector escape magnet Est being operated, willcause the side switch wipers 17, 18, 19, 20, 21 and 22 to advance fromtheir first or normal position of rest to their second position which istheir first operative position. In this second position the circuitextending back to the contact 46 of the selector switch is still furtherbroken by the opening of the first position contacts of the side switchwiper 19.

The subscriber now operating his interrupter 1 for the second time, willsend a second series of impulses of a predetermined known number tovibrate the fast armature 59 of the twoar1nature relay 15, the slowarmature 60 thereof during the sending of these impulses remaining inits normal position. Upon the first interruption of the line circuit bythe subscriber, the slow operating armature 60' instantly returns to itsnormal position, where it remains throughout the sending of thefollowing current impulses. Then upon each det-raction of the fastarmature 59, a circuit is completed through the second position contactsof the side Switch relay, and normally opened contacts 57 of the rapidoperating armature 59' of the relay 15. Each operation of the armature59 closing the contacts 57, causes the primary stepping magnet PS toadvance the connector switch" wipers 27, 28 and 62 from one level toanother level of connector switch contact banks. i

It may be seen that at the time through normal contacts 51 of thevibrating armature 59, that the circuit of the release magtacts' 51 atthis time.

magnet PS.

net BL is closed for very brief interyals, but'this release magnet isniade so that it is slow operating, that is,'sluggish of move ment, andit will notrespond to impulses or such short duration as would'be causedby the rapid intermittentclosures the con- At the endot the firstseriesof impulses,

the connector switch wipers will have been advanced a 'certain nurnberofsteps dependupon the'variable or predetermined operation of thesubscribers instrument interrupter, and the operation by the subscriber'ending, the last impulse will be continued by a prolonged impulselaeting'until the next operation or" the subscribers circuitinterrupter 1. Upon this prolonged impulse, the slow acting armaturewill be also attracted, and a circuit will be coi'nple'ted' includingthe second position contacts ofthe side switch wiper 21 fortheescapeinagnetEs0 of the connector switch, said circuit includingnormally opened contacts 57 and 58 of the relay 15, off-normal 'contacts63, the 'saidsecond position contacts of the sideswitch wiper21, thewinding of the escape magnet E86 and the central office source ofcurrent, which source will cause the, operation of the said escapemagnet to cause theside switch wipers 17 18, 19, 20, 21 and 22tobeadvanced into their third position. Whenth'e sideswitch wiper 20isadv'anced into third position, the

secondary stepping magnet SS is substituted into the circuit for "theprimary stepping The subscriber again operating his circuit interrupter,will cause the immediate retrac- 'tio n, of thearmature 60wliere it willremain 'thrdughout the following series of impulses,

and the arinature59 will be vibrated with the impulses as beforedescribed, to cause at this time the operation of the steppingsecoiidary magnet SS in the same manner as before described for theprimary stepping net SS being intermittently actuated, will stepftheconnector switch wipers 27, 28 and 62 from one set of linecontactstonnother set of line contacts in the levelfpreviously selected.When the subscriber predetermined number of impulses in thisseries hasbeen sent, the connector switch wipers will be resting upon the linecontacts 25, 26 and 65 of the called-for line. The last subscriber sentimpulse will be a prolonged or continued impulse, *so that botharmatures "of the relay 15 willbe' again operated, the

slow acting armature 60 responding only after a short period of. time.

; If 'thecalled-for line is not busy, this fact will be indicatedby thepresence or absence of a direct connection 'totheground pole' of batteryleading to the j [contact 65 of the calledt'or line. Otherwise therewould only be connected to this contact 65, the negative pole of thesource of current leading to itsconta'ct 65,'thro'ugh the winding of thelocal line magnet 29lfor the calling line. For the moment we willconsider that the called-for lir'ie is busy and that in'amann'er whichwill be later described in detail, the ground pole ottlie sourceofcurrenthas been previously connect'edto the contact 65 of the called-forline. .Thc-eonneewr switch wiper 62 making contact with t'his groundedcontact 65, will "thereupon extendits ground connection to the point 66inthe circuit indicatedin the drawing, thereby coinpletin'ga shortcircuit about, the winding of the relay. 67, known as-the test relay, topreventits operation. This relay 67 will be thereby prevented fromestablishing a short circuit about the winding '68, by the operatidn ofthe contact 69 of the relay 67 and the contact 69jtl1erefore remaininopen, the relay 68 will remain un- .Esc to the negative pole of thesource of current. The winding of therelay68 is of a very highresistancecontaining a large number of turns of very finewire, so thatthe current flowing over this circuit willbe limited'in value topreventthe operation of the escape magnet'Esc", which requiresarelatively large amount of current to opcrate. The high resistance relay68', however, by virtue of its adjustment aiid'large numberof turns,will be operated to apply the busy-tone signal to the calling lineconductors. The busy-tonesignal is produced by the interrupter 31 andthe central ofiice source of current through the said interrupter andawinding of the induction coil .71. The current flowing through the saidwinding will induce a current in the secr a, b ondary winding'ot theinduction "coil 71,

the induced current flowing from the ground pole of the source ofcurrent, through the said secondary w1nd1ng,1iormal contacts 72 of therelay 67, the condenser 73, now closed contacts 74 of the relay 68,circuit conductor 75 which is connected to the line conductor 2 of thecalling line, through the selector switch contacts 35 1'54 and fourthposition contacts of the selector side 's'witchfwiper 5 andtheassociated line finder contacts 3-1, the circuit being completedthroughthe subscribers telephoneand returning through the line conductor .1,which is extended through the line finder contacts l -3, fourth positioncontacts of the selector side switch 1 volved being later described inthis armature relay 15.

wiper 6, selector switch contacts 86-55, returning to ground through thewindings 76 and 78 of the relay 16 and the battery feed coil 78. Thiscurrent flowing over the calling subscribers line and through hisinstrument, will produce a characteristic tone in the callingsubscribers receiver, known as theb usy-tone. The calling subscriberhearing this tone will know that the called-for line is busy andreplaces his receiver uponthe hook, restoring the interconnectingapparatu's'to normal position, the manner of release of the switches andconnections" innarrative.

Assuming now that the called-for line is notbusy, there will be noground connected to the contact 65 of the called-for line and currentfrom the central ofiice source of current will flow through the localmagnet 29 of the called line, through the connector switch contacts62-65 and through the third position contacts of side switch wiper 22,and through the relay 67 tooperate the relay 67 and. energize thelocalline magnet 29. The operation of the magnet 29 is to dissociate thecalling, or line finder apparatus,

from the circuit of the line in any suitable manner, such dissociationbeing well understood. The operation of the relay 67 will produce ashort circuit about the relay 68 by virtue of the shunting contact 69,now closed, and the operation of the relay 68 will -'be prevented. Theescape magnet E802, will now be operated over a circult including theconnects the ground pole of the source of current to the contacts 65 ofthe called-line through the connector switch wiper 62, thus to producethe busy condition of the contacts 65 which are understood to bemultipled to like contacts 65 of other connector switches, this beingwell understood in the art. The presence of this ground will prevent theintrusion of other calling lines into the connection.

The side switch wiper 2O advancing into its fourth position, willdissociate the secondary stepping magnet SS from its operative circuitrelation withthe stepping contacts 57' of the two-armature relay 15. Theconnector side switch wipers 17 and 18 in their fourth position,complete a circuit for the ringing generator 30, the said circuitincluding the signal bell 79 of the called-for line subscriber. Thiscircuit is traced as connector switch contacts 28- 26, the lineconductor 24 of the called line, signal bell 79, condenser 80, the lineconductor 28, connector switch contacts 2725, fourth position contactsof the side switch wiper 17, the

winding of the ringing trip relay 81, the

resistance lamp 82, the circuit being alternately completed by therotation of the interrupter Y to the negative pole of the source ofcurrent, through the resistance coil 83, or depending upon the positionof the rotating interrupter Y, through the ringing generator 30, to the:negative pole of the source of current. The ringing generator 30 willproject. ringing current over the line intermittently until thecalled-for subscriber responds. Upon the response of the calledforsubscriber, current from the central office source of direct currentwill flow over the circuit through the responding subscriberstransmitter and through the trip relay 81, to

cause the operation of the said trip relay.

This trip relay thereupon closes its contacts 85, which will complete acircuit for the escape magnet. E802, this circuit being traced from thenegative pole of the source of current through the winding of the escapemagnet, the fourth position contacts of the connector side switch wiper21, the now closed contacts 85 of the trip relay 81 and now closedcontacts 57 and 58 of the two-armav ture relay 15, to the ground pole ofthe source of current. Current from this source will operate the escapemagnet E802, to cause the connector side switch wipers 17-22, in-

clusive, to advance from their fourth to fifth, or ultimate operativeposition. In

this ultimate operative position, the side switch wipers 17 and 18 willcomplete a talking circuit extending between the talk-' ing conductors 1and 2 of the calling line to the talkingconductors 28-24 of the calledline, so that the subscribers may now converse, talking battery beingsupp-lied for the calling line through the windings of the relay 16, andfor the called line through the windings of the battery feed coil 78,the

talking circuit extending through condensers 86 and 87.

By the opening of the fourth position contacts of the side switch wipers17 and 18, the ringing circuit is interrupted."The side. switch wiper 22passing from fourth to fifth position continues the connection togroundto thetest contact of the called line. The circuitof the escape magnetis interrupted by the passing of the side switchwiper 21 from positionetc position 5. The subscribers now being in conversational circuit willconverse, and uponretiring, the calling subscriber will open the circuitof his line by opening the contact a at his instrument, therebyreleasing the serially connected relay 16 which will open its contacts56 in the circuit of the twoarinature relay 15. This causes thedisconnection to take place, andthe release of the selector andconnector switches, and circuits and apparatus involved. The twoarmatures of the relay 1 5 will be restored to normal, and a circuitwill be completed through contacts 51 of the relay 15 for the releasemagnet R-L of the connectorswitch. The circuit of the release magnet RLbeing established for asufiiciently long and predetermined period, thesluggish release magnet RL will have time to operate its armatures tocause the release of the selector switch, together with its associatedside switch wipers and line connecting wipers, the means for do-ingthisbeing well known and understood in the art to which this inventionappertains.

The operation of the release magnet BL is continued until all of theapparatus is fully restored to normal by virtue of the locking circuit,consisting of contacts 90 of the release magnet which are closed uponits operation and off-normal contacts 91 in this locking circuit. Thecontacts 91 are arranged to be opened only when all of the apparatus hasbeen restored to normal position, so that th release magnet RIF, untilthis occurs, causes the releasemechanism to remain fully actuated. Atthe same time the release magnet RL for the selector switch is operated,the circuit for operating the release magnet EL of the selector switchbeing traced from the ground pole of battery through the second, winding95,- now closed contacts 92 of the connector switch for the winding ofthis release magnet in cluding contacts 96 of the magnet RL, cit normalcontacts 42- of the selector switch, the circuit leading therefromdirectly through the selector switch contacts 37-4=6,

and now made contacts 92- of the connector switch, release magnet,through the winding 95 thereof, to the ground pole of battery. Theoff-normal contacts 42 ofthe selector switch are adapted to be, openedonly when all of the rest of the apparatus of the selector switch hasbeen restored to its normal position, the actuation of the releasemagnet BL causing such restoral in any wel'llniown manner. The functionof the serially included winding 95 of the connector switch releasemagnet is to provide for the continued operation o'l. this magnetinsuring continued closure of the contacts 92 in the circuit of selectorswitch release magnet switch, until the selector switch mechanism aswell as the connector switch mechanism has been restored to normal.Thus, a positive restoral of all of the ap paratus of the connector andselector switches is provided. When the side switch wipers 9 and 10 ofthe selector switch have been restored to normal position, a, circuit isprovided for the disconnect apparatus of the finder switch not shownextended from the ground pole of battery through normal contacts 3%, ofthe selector impulse relay 7, and first position contacts or the sideswitch wipers 9 and 10 to the tinder switch release magnet not shown butw ll understood in the art.

lVhat I claim is z- 1. In a telephon system, a line, an automatic switchaccessible to said line, and means "for controlling the said switch byimpulses delivered over the two sides of the said line in series, saidmeans comprising a two-armature relay, one of the said armature-s beingresponsive to all of the impulses of a series, a second armaturelor thesaid relay responsive only to the linal impulse of the series, andsteering means for the said switch controlled jointly by the said firstand second armatures.

2. In a telephone system, a line, an automatic switch accessible tosaid, line, switch wipers for the said switch, controlling means for thesaid switch wipers, means for controlling the movements of the saidwitch by impulses delivered over the two sides of the said line inseries, said means including a relay having a plurality of armatures,one of the said armatures being responsive to all of the impulses of aseries, another of the said armatures being responsive only to the finalimpulse of the series, said controlling means being under the jointcontrol of the said armatures.

3. In a telephone system, an automatic switch having primary andsecondary operating magnets and a release magnet, a relay having anarmature for directively controlling said operating magnets, a secondarmature for the said relay for controlling the change over from oneoperating magnet to the other, and means operative under the ointcontrol of both of the said armatures to close and energize the circuitlot) of the said armatures controlling the operating movements of thesaid switch, a second armature controlling the change over from oneoperating movement to the other, the first armature being responsive toshort and prolonged impulses of current, and the second armature beingresponsive to only prolonged impulses of current, and means at thesubstation for producing short impulses and prolonged impulses ofcurrent, whereby the connection to another line may be established bythe said switch.

5. In a telephone system, a subscribers line, an automatic switch havingprimary and secondary operating movements, and re lease means, means forextending said line to said switch, a relay for the said switch having aplurality of armatures, one of the said armatures controlling theoperating movements of the said switch, a second armature controllingthe change over from one operating movement to the other, the firstarmature being responsive to short and prolonged impulses of current,and the second armature being responsive to only prolonged impulses ofcurrent, means at tie substation for producing short impulses andprolonged impulses 01": current, whereby the connection to another linemay be established by the said switch, and releasing means "for the saidswitch under the control 01 one of the said armatures, the saidreleasing means being operative only on a prolonged current flow andirresponsive to short impulses of current, whereby connection to theother line may be disestablished.

6. In a machine switching telephone system, the combination with aselector, a stepping relay associated therewith, a sender for operatingthe same, a release circuit for the said selector, a primary steppingcircuit controlled by an armature ot' the said relay, a secondarystepping circuit, a slow acting armature tor the said relay adapted toshift the control of the said first named armature from the primarystepping circuit to the secondary stepping circuit whereby the saidfirst-named armature will on a first series of impulses control thestepping of the said selector in a primary direction, and at the end ofthe said series of impulses will be adapted to control the stepping ofsaid selector in a secondary direction.

'7. In a switch system for interconnecting lines, a current source, aswitch for performing operations of different characters, a controllingrelay for controlling the amount of an operation performed by the saidswitch, a primary circuit for enabling the switch to perform oneoperation, a secondary circuit for enabling the switch to performanother operation, a change over circuit for transferring the action ofthe said controlling relay from the primary circuitto the secondarycircuit, a change-over tures adapted to be included in the saidchange-over circuit to operate the said change-over electromagnet.

8. In an automatic telephone system, the combination with a selectorswitch and a connector switch, means to cause the selector switch toassume a connector select- .mg position, a release magnet for the saidselector switch to cause it to be restored to its normal position, meansto cause the said connector switch to assume a line selecting position,a release magnet to restore the said connector switch to itsnormalposition, and a releasing circuit for the said selector switch releasemagnet including its winding and normally opened contact there of, anotf-normal contact of the said selector switch, a selector switch wiper,an associated connector switch contact and a normally opened contact ofthe said connector illl switch release magnet, a winding thereof,

and a source of current whereby the said connector switch release magnetand the aid selector switch release magnet will both remain energizeduntil the said selector switch has been released.

9. In a telephone system, atelephone line, an automatic switchaccessible to said line, means for controlling said switch by impulsesdelivered over the two sides of said line in series, said meansincluding a single electromagnetic device having armatures, one of saidarmatures being responsive to individual impulses of the series, and theother being responsive at the close of the series of impulses, and acircuit controlling device for said "switch controlled jointly by saidarmatures.

10. In a telephone system, lines divided into groups, an automaticswitch having motion in one plane to select groups, and motion in aplane at right angles thereto to lind a line in aselected group, meansincluding arelay for controlling the operation of said switch a singleenergizing winding for said relay, means responsive to impulses over thetwo sides of a line circuit in series for energizing said winding, meansfor rapidly interrupting said ,line circuit to generate impulses, meanswhereby one of said arma-tures responds to said interruptions, and meansfor maintaining the other of said armatures in a stationary positionduring the transmission of said impulses.

11. In a telephone system, an incoming line, outgoing lines, a twomotion switch for interconnecting said incoming line with any of saidoutgoing lines, a relay responsive to impulses transmitted over saidincoming line,said relay having contacts and two armatures operated outof synchronism to control the same, a magnet for controlling themovements of said switch, and a circuit for said magnet extendingserially through contacts controlled by said armatures.

12. In a telephone system, an incoming line, outgoing lines, a twomotion switch for interconnecting said incoming line with anyofisaid'outgoing lines, a relay having two sets of contacts controlledover said incomingli'ne, one set of contactsbeing operated in responseto each impulse of a series, and the otherset of contacts being operatedin response to the last impulse of a series, a magnet for controllingthe movements of said" switch, and a circuit for said magnet extendingserially through contacts "controlled by said "armatures.

13. In a telephone system, an incoming line, a plurality of outgoinglines, a switch for extending said incoming line to any of said outgoinglines, a relay responsive to impulses transmitted over said incomingline, said relay having armatures operating out of synchronism, primaryand secondary operating devices for said switch, a circuit controllingmechanism for causlng the operation of said devices in proper sequence,releasing mechanism for said switch, and circuits for said devices, andmechanisms con: trolled at the armatures of said relay.

14. In an automatic telephone system, two subscribers stations, anautomatic mechanism for establishing connection between the sameinvolving a calling station and an impulse transmitter, and means forestablishing said connection by impulses from said transmitter, agenerator circuit normally disconnected from connected stations, a relayresponsive to interruptions in the line circuit, said relay having fastand slow operating armatures, a circuit controlling device forconnecting said generator circuit into the connected line circuit, andan operating circuit for said circuit controlling device controlledjointly at the armatures of said relay.

15. In a telephone system, in combination with a connector switch, arelay for controlling the operation of the said switch, said relayhaving a plurality of armatures in multiple magnetic circuits, a singlewinding only for the said relay to energize the said multiple magneticcircuits, a circuit comprising a source of current and a circuitinterrupter for the said winding, means responsive to the operation ofthe said circuit interrupter to transmit a series of current impulsesthrough the winding of the said relay, and circuit connections under thecontrol of the said two armatures adapted to operate the connectorswitch in a primary manner upon a first operation of the said circuitinterrupterand in a secondary manner upon a second operation ofthe-saidcircuit interrupter.

16. In'a telephone system, in combination with a connector switch, adouble armature relay for controllingthe said switch in primary andsecondary movements, a single energizing winding for thesaid relay, acircuitifor the said winding comprising a source of current and acircuit in'terrupter, meansresponsive to the operation or the saidcircuit interrupter totransmit a series of current impulses through thewinding of the'said relay, one of the said armatures being responsive tovibrate substantially in unison with the said current impulses and theother armature being responsive only to the last current impulse of theseries.

17. In a telephone system, in combination with a connector switch, adouble armature relay for controlling the said switch in primary andsecondary movements, :1- single energizing winding for the said relay, acircuit for the said winding comprising a source of current and acircuit interrupter, means responsive to the operation of the saidcircuit interrupter to transmit a series of current impulses through thewinding of the said relay, one of the said armatures being responsive tovibrate substantially in unison with the said current impulses and theother armature being responsive only to the last current impulse of theseries, the said vibrating first armature controlling the extent ofmovement of the said connector switch and the other armature controllingthe character of switch movement.

18. In a telephone system, an automatic switch having a primary movementto select groups and a secondary movement to find a line in a selectedgroup, means including a relay for controlling the operation of the saidswitch, said relay having a pair of armatures, the operation of one ofthe said armatures being sluggish as compared with the operation of theother armature, the first armature controlling the extent of primary andthe extent of secondary movement and the other armature operatingbetween the said primary and the said sec ondary switch movements toshift the control of the first armature over the said switch so as tocause it upon a subsequent operation to move in a secondary manner.

19, In an automatic telephone system, the combination with a connectorswitch for making connection with a desired called telephone line, aprimary magnet, a sec ondary magnet, a controlling relay for the saidswitch, said relay having a pair of armatures, a calling line adapted tobe associated with the said relay to control the said connector switch,a commutator for the said calling line adapted to produce successiveseries of calling line interruptions, one of the said armatures beingresponsive to each following circuit closure after each circuitinterruption, the other of the said armatures being responsive only tothe final prolonged closure after each manner respectively, each underthe successive control of the said first armature, and circuitconnections whereby the control of the said first armature over theprimary magnet is secured by a first operation of the said distributorswitch, and whereby the control of the said first armature is shiftedfrom the said primary magnet to the secondary magnet upon a secondoperation of the said distributor switch.

20. In a telephone exchange system, an incoming line, a switch forextending said line, primary and secondary stepping mags nets foroperating said switch, an escape magnet for controlling the operation ofsaid secondary stepping magnet, and'a relay connected to said incomingline, said relay having contacts in the circuits of said primary andescape magnets, the contact in the circuit of said escape magnet beingclosed upon energization'of said relay.

In witness whereof, I hereunto subscribe my name this 12th day of April,A.

D. 1918. a ,i I

a [FRANK M. SLOUGI-LW

